1. Field of the Invention
The present invention relates to a magnetic recording medium. More specifically, it relates to a magnetic recording medium having an improved reproduction output and a process for the production thereof.
2. Discussion of Related Art
With an increase in a demand for high-density recording, vigorous technical improvements have been advancing in a variety of fields of optical recording, semiconductor memory, etc. In particular, in the field of magnetic recording, magnetic thin layers of Co--Ni, etc., as a substitute for conventional magnetic powder-coated recording media are now vigorously being studied as a high-density recording material.
Further, recently there has been a trend from a conventional longitudinal recording method to a perpendicular recording method to achieve still higher-density recording. In this recording method, a demagnetizing field effecting recorded magnetization decreases with an increase in recording density. Therefore, this method is said to be, in principle, suitable for high-density recording.
A Co--Cr alloy thin layer has been widely studied as an ordinary material for a perpendicular recording medium, while a Co--O perpendicular magnetic thin layer such as disclosed in Japanese Unexamined Patent Publication No. 59-140629 is being generally studied as a material for a perpendicular magnetic recording tape.
In the beginning, the above thin layer has been formed by a method in which Co vapor is deposited onto a substrate surface nearly perpendicularly while an oxygen gas is introduced into a layer-forming atmosphere. In the layer formed by this method, the principal axis of magnetic anisotropy is nearly perpendicular to the layer surface, and such a structure has been considered to be optimum for perpendicular recording.
Although there has been a recent attempt to increase a reproduced output by tilting the principal axis of magnetic anisotropy from a normal of the layer surface, it cannot be said that a value of the reproduced output is sufficient for practical use.